A canister type vacuum cleaner is illustrated in the patents incorporated by reference herein and includes a reduced velocity chamber with a high velocity air inlet. Air is drawn into the chamber by an electric motor which drives a rotary means, or fan, for creating vacuum in the chamber to draw air laden with particulate material through the chamber and force it from the outlet as exhausted clean air. Canister type vacuum cleaners normally include a conical filter extending downwardly into the canister or low velocity chamber and formed of a porous mat to remove the dirt and debris carried by the air coming into the canister. The high velocity air drawn into the chamber has a tendency to entrain large solid particles which are brought into the low velocity chamber where the air is then swirled or vortexed in a centrifuge configuration with convolutions so that large particles carried into the chamber with the inlet air are extracted by the vortexed or cyclonic action of the air in the canister. Thereafter, the air is pulled upwardly through the conical filter mat or porous layer toward an upper motor that drives a fan for creating a vacuum in the canister, or reduced velocity chamber, so that the air flowing upwardly through the conical filter passes through a filter disc and outwardly through an exhaust passage, or passages, above the canister.
The canister type vacuum cleaner, as so far described, cannot efficiently remove gaseous impurities, such as paint fumes and other odor creating gases which are entrained in the air and pass through the vacuum cleaner. Such gaseous materials, or fumes, are sometimes flammable and can be ignited by the sparks of the motor driving the vacuum cleaner. This is a problem associated with all vacuum cleaners in general. For that reason, vacuum cleaners are used for removing debris from carpets, draperies and other surfaces, but are not generally employed for the purpose of removing fumes and gaseous impurities from ambient air. It has been suggested that a filter could be employed in the exhaust area as a separate canister to remove gaseous contaminants of the air exhausting from the vacuum cleaner. This concept, which has not been widely employed, still allows the fumes to be in contact with the sparks of the electric motor driving the vacuum cleaner. In addition, the use of activated charcoal for removing gas has not been attempted internally of vacuum cleaners and particularly not in canister type vacuum cleaners because the particles of carbon which form the activated charcoal type of filtering elements are extremely flammable and were heretofore believed to be inappropriate for use in the low velocity chamber of a vacuum cleaner.
This chamber is in the path of air flowing through the vacuum cleaner upstream or prior to the vacuum cleaner driving electric motor; consequently, carbon particles introduced by the filter element would provide an apparent problem at the motor area.
In summary, vacuum cleaners, in general, and canister type vacuum cleaners, in specific, have not heretofore been adapted for uses which would encounter explosive and/or noxious gases or fumes entrained in the air passing through the vacuum cleaner.